The lights are blazing from the world's largest floating Christmas tree -- a gigantic metal structure as tall as a 27-storey tower block set on a lagoon in Rio de Janeiro.

With the mountain-top Christ the Redeemer statue looking down on it, the 82-meter tree stands as a brightly flashing symbol of peace in one of the world's most violent cities.

"We're competing with all the violent news from Rio to show the world what a marvelous city it is," Roberto Medina, the project's creator, told reporters during a boat tour on the Rodrigo Freitas lagoon on Tuesday night.

The tree features moving images of church bells and doves flickering from nearly 3 million lights.

The Christmas tree, first erected in 1996, constitutes Rio de Janeiro's third biggest tourist event after the pre-lenten Carnival and New Year's Eve on Copacabana and other beaches.

Some 100,000 people came to watch on Saturday night when the lights were switched on and more than a million are expected to view the structure before the lights are turned off on Jan. 6.

"It's beautiful. Rio isn't just shootings and killings," said Sandra Gomes de Faria, a 51-year-old retired telephone operator.

Around 1,300 workers were hired to assemble the tree, constructed from 410 tons of metal scaffolding supported by 11 barges.

Bradesco Seguros e Previdencia, Brazil's largest insurance company, spent 2 million reais on the project.

The Guinness Book of Records lists it as the world's largest floating Christmas tree.

In comparison, the Christmas tree in New York's Rockefeller Center is 71 feet tall and has 30,000 lights, although it is a real Norwegian spruce.

Rio, which has one of the world's highest murder rates, was rocked by violence last week as rival drug gangs fought for control of drug distribution points in city slums.

(Agencies)